Move the new review request approval tests into its own class.
Review Request #9241 - Created Oct. 3, 2017 and submitted
The newly-introduced review request approval tests were living in the
issue counter tests, which wasn't the correct place for them. This moves
them into their own test suite, updating them to not depend on the
internals of the issue counter tests, and changes the docstrings to be
more consistent with the other review request tests.
Unit tests pass.